Correcting fluid with drying indicator

ABSTRACT

A correcting fluid with a colored drying indicator that includes as fluorescent dye, sodium 8-hydroxy-1,3,6-pyrenetrisulfonate and a good solvent for the fluorescent dye, in which the solubility of the fluorescent dye at 20° C. is at least equal to 0.1 g/l, and, a poor solvent for the fluorescent dye, in which the solubility of the fluorescent dye is less than or equal to 0.01 g/l at 20° C., the poor solvent being miscible with the good solvent for the fluorescent dye.

CROSS REFERENCE TO RELATED APPLICATION

This is a national stage application of International Application No.PCT/FR2007/052433, filed on Dec. 11, 2006, the entire contents of whichApplicants incorporate herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The embodiments of the present invention relate to a correcting fluidcontaining a fluorescent dye as drying indicator.

Water-based or volatile organic solvent-based correcting fluids forhiding writing errors and then writing over them, if so desired, on thedried correcting film, are available on the market. Although water-basedfluids are generally preferred for their greater harmlessness, theynevertheless have the drawback, when compared with solvent-basedcorrecting fluids, of drying much less quickly than the latter. Itgenerally takes several tens of seconds before the film can beoverwritten without damaging it. A user who is in a hurry, and who hasno indication informing him of the progress of the drying, is liable toattempt to overwrite on the masking film too soon.

It is a known practice to add drying or visualization indicators topaperware compositions whose use involves a drying time afterapplication, such as correcting fluids.

The drying indicators used in correcting fluids are intended to allowthe user to evaluate visually the moment at which the composition issufficiently dry, i.e. the moment at which the film formed by thecorrecting fluid can receive new inscription without the risk of beingdamaged.

Drying indicators, which are colored and thus visible to the user at thetime of application of the composition, gradually lose their color andideally become totally colorless when the composition is dry.

Thus, patent application US 2005/0075419 discloses a water-basedcorrecting fluid containing, as drying indicator, a colored pHindicator. The correcting fluid also contains a volatile acid or avolatile base whose evaporation leads to a change in the pH of thecorrecting film and consequently to decolorization of the pH indicator.

The problem of compositions containing a colored pH indicator as dryingindicator is that of precise adjustment of the decolorization time tothe real drying time of the composition. Specifically, when the pH ofthe composition changes too quickly and the indicator becomesdecolorized before the composition is fully dry, the user is led inerror and early overwriting of the film will cause it to be damaged.Conversely, when the pH variation and the decolorization of theindicator do not take place until a certain time after the total dryingof the composition, the user needlessly delays the moment of overwritingand thus wastes time.

The drying time of a film of correcting fluid depends on severalparameters such as

-   -   the rate of evaporation (volatility) of the solvents,    -   the speed of penetration of the solvents into the paper, which        depends essentially on the surface tension of the fluid, the        viscosity of the fluid and the surface energy of the support,        and    -   the speed of formation of the film.

In the context of its research aimed at solving this problem of preciseadjustment of the drying time to the decolorization time of correctingfluids, the Applicant has discovered that it is possible to very finelymodulate the decolorization time of certain fluorescent dyes by usingthem in a system of mutually miscible solvents, formed from at least one“good” solvent for the dye and at least one “poor” solvent for said dye.

SUMMARY OF THE INVENTION

Consequently, one embodiment of the present invention is a correctingfluid with a colored drying indicator, comprising:

(a) as fluorescent dye, sodium 8-hydroxy-1,3,6-pyrenetrisulfonate and

(b) a good solvent for the fluorescent dye, preferably having a boilingpoint of less than or equal to 100° C., and, preferably,

(c) a poor solvent for the fluorescent dye, which is miscible with thegood solvent (b) for the fluorescent dye.

DETAILED DESCRIPTION OF THE INVENTION

Sodium 8-hydroxy-1,3,6-pyrenesulfonate, also known as Solvent Green 7 orpyranine (CAS 6358-69-6, Color Index No. 59040) is a green-yellow dyethat is approved by the FDA as a dye for cosmetic compositions. This dyeis not included among colored pH indicators. Specifically, it preferablyhas, over the whole pH range, a fluorescence emission whosecharacteristics vary too gradually for them to be able to serve as pHindicators.

The capacity of this dye to serve as a drying indicator in thecompositions of the embodiments of the present invention is thereforenot associated with its state of protonation/deprotonation, but, amongothers, with its solvatochromism in relation with its state of solvationin the solvent mixture of the composition.

Specifically, the Applicant has found that sodium8-hydroxy-1,3,6-pyrenetrisulfonate, dissolved in a “good” solvent asdefined below, is characterized by high fluorescence intensity whichdecreases when this good solvent is mixed with a certain proportion of a“poor” solvent for the dye, as described below.

The Applicant has also found that when the good solvent used is water,the addition of an organic solvent chosen from poor solvents for thefluorescent dye is reflected by a change, generally an acceleration, inthe speed of penetration of the solvent phase into the paper supportonto which the correcting fluid is applied, and that this accelerationof the penetration speed in turn has repercussions on the speed ofdrying of the film and the speed of decolorization of the dye.

The idea thus emerged of dissolving this fluorescent dye in a solventphase containing a mixture of these two types of solvent, so as tomodify the state of dissolution of the dye and/or the speed ofpenetration into the paper support in an attempt to adjust thedecolorization time of the fluorescent dye precisely to the drying timeof the film of correcting fluid. The Applicant has thus found that anastute choice of the good and poor solvents as a function of theirvolatility and of their solvating power for the dye, but above all thevariation of the respective proportions of the good and poor solvents inthe compositions of the embodiments of the present invention, makes itpossible to very finely adjust the decolorization time of thefluorescent dye to the real drying time of the deposited film.

Although the above explanations suggest that the presence of a “poor”solvent in the compositions of the embodiments of the present inventionis an essential technical characteristic of the correcting fluidsaccording to the embodiments of the present invention, a person skilledin the art will understand that, in certain particular cases, whenevaporation of only the good solvent for the fluorescent dye bringsabout its decolorization in coordination with the drying time of thecomposition, the addition of a poor solvent is superfluous. The presenceof a poor solvent in combination with a good solvent is thus,admittedly, generally desirable, but nevertheless constitutes apreferred optional characteristic of the compositions of the embodimentsof the present invention.

In an embodiment of the present invention, the term “good solvent” meansa solvent in which the solubility of the fluorescent dye at 20° C. is atleast equal to 0.1 g/l. The term “poor solvent” denotes organic solventsin which the solubility of the fluorescent dye is less than or equal to0.01 g/l at 20° C.

As indicated hereinabove, the good solvent has a boiling point of lessthan or equal to 100° C. Needless to say, this good solvent ispreferably water, chosen for its total harmlessness and its very lowcost. Demineralized water is preferred in particular. The upper limit ofthe boiling point (100° C.) is dictated only by the drying time of thecomposition. Beyond a boiling point of 100° C., the good solvent, whichconstitutes the majority of the composition, would take an excessivelylong time to evaporate, which would lead to an undesirable lengtheningof the drying time of the film.

The poor solvent must be miscible with the good solvent for thefluorescent dye. The good and poor solvents do not necessarily need tobe mutually miscible in all proportions, but their miscibility must beensured at least for the good solvent/poor solvent ratios of thecorrecting fluid before application and during the drying step.

Examples of preferred poor solvents that may be mentioned include C4-6alkylene glycols such as butylene glycol and hexylene glycol, C2-4 loweralcohols such as ethanol, n-propanol, isopropanol, n-butanol andisobutanol, and dioxane.

As explained hereinabove, the decolorization time of the fluorescentdyes may be adjusted to the drying time of the compositions of theembodiments of the present invention by adding a relatively small amountof one or more poor solvents, of the order of only a few percent. Theweight ratio of the good solvent to the poor solvent in the compositionsof the embodiments of the present invention is preferably between 99/1and 80/20 and in particular between 98/2 and 90/10.

The composition according to the embodiments of the present inventionpreferably has a basic pH, advantageously between 7 and 11 andpreferably between 7.5 and 10. In this pH range, the fluorescenceintensity of the fluorescent dye is, specifically, particularly high andthe decolorization at the time of drying of the applied film is readilydetectable by the human eye. This pH may be adjusted by adding any base,not necessarily a volatile base. Examples of such bases that may bementioned include ammonia, triethanolamine and 2-amino-1-methylpropanol(AMP). The pH of the compositions according to the invention mayoptionally be fixed by means of a suitable buffer.

The concentration of the fluorescent dye in the correcting fluids of theembodiments of the present invention is preferably between 0.01% and 1%by weight and in particular between 0.1% and 0.5% by weight, relative tothe total weight of the composition.

The correcting fluid of the embodiments of the present inventioncontains, in addition to the fluorescent dye and the solvent phasedescribed above, one or more adjuvants commonly used in this type ofcomposition, chosen, for example, from film-forming polymers, fillers,opacifying pigments, preferably white pigments such as titanium dioxide,optical brighteners, dyes, antifreezes such as glycerol, surfactants andpreserving agents.

Examples

Composition A (without Poor Solvent)

0.15% by weight of Solvent Green 7, sold under the name Jaune Pyracide Gby the company Colorey, is added to a standard correcting fluid (basefluid) having the following composition:

Distilled water 10% Resin (acrylic latex 35% solids) 25% TiO2 37% CaCO313% Base qs pH 8-8.5 Other additives 12% (preserving agents, antifoam,surfactant, optical brightener)

A film about 75 μm thick is applied to standardized paper (Baumgartnerpaper ISO 12757) using a hand coater. The film is allowed to dry at atemperature of 20° C., and the time after which it is possible tooverwrite on the dried film with a ballpoint pen (=drying time) is thennoted.

The decolorization time of the fluorescent dye is estimated by visualevaluation or alternatively by colorimetry (L*a*b* system).

A drying time of the film of about 1 minute and a decolorization time ofabout 3 minutes are thus determined for composition A. This result isunsatisfactory because, if the user waits until the film has fullydecolorized before overwriting it, he needlessly wastes about 2 minutes.

Compositions B and C (with poor solvent)

4.00% hexylene glycol (Composition B) and 4.00% n-propanol (CompositionC) are added, respectively, to composition A containing 99.85% basefluid and 0.15% Solvent Green 7.

When the drying time and the decolorization time of these twocompositions are measured under the same conditions as for CompositionA, the following results are obtained:

Composition B:

Drying time: 1 minute

Decolorization time: 1 minute 10 seconds

Composition C:

Drying time: 50 seconds

Decolorization time: 1 minute 10 seconds

It is found that, for the two compositions, the difference between thedrying time and the decolorization time is substantially reduced whencompared with that observed for Composition A free of secondary solvent(“poor” solvent). It may moreover be observed that the addition, to thewater-based composition, of a small amount (4%) of hexylene glycol(boiling point of 197° C.) does not increase the drying time of thefinal composition. On the other hand, the addition of only 4% of a poorsolvent that is relatively more volatile than water (n-propanol, boilingpoint of 97° C.) advantageously reduces the drying time of thiswater-based formulation (Composition C) by about 20%.

1. A correcting fluid with a colored drying indicator, comprising: (a)as fluorescent dye, sodium 8-hydroxy-1,3,6-pyrenetrisulfonate and (b) agood solvent for the fluorescent dye, in which the solubility of thefluorescent dye at 20° C. is at least equal to 0.1 g/l, and, (c) a poorsolvent for the fluorescent dye, in which the solubility of thefluorescent dye is less than or equal to 0.01 g/l at 20° C., the poorsolvent being miscible with the good solvent (b) for the fluorescentdye, wherein the correcting fluid includes at least one opacifyingpigment.
 2. The correcting fluid according to claim 1, wherein the goodsolvent has a boiling point of less than or equal to 100° C.
 3. Thecorrecting fluid according to claim 1, wherein the concentration of thefluorescent dye is between 0.01% and 1% by weight relative to the totalweight of the composition.
 4. The correcting fluid according to claim 3,wherein the concentration of the fluorescent dye is between 0.1% and0.5% by weight relative to the total weight of the composition.
 5. Thecorrecting fluid according to claim 1, wherein the good solvent iswater.
 6. The correcting fluid according to claim 1, wherein the poorsolvent is selected from C₄₋₆ alkylene glycols, C₂₋₄ lower alcohols anddioxane.
 7. The correcting fluid according to claim 1, wherein theweight ratio of the good solvent to the poor solvent is between 99/1 and80/20.
 8. The correcting fluid according to claim 7, wherein the weightratio of the good solvent to the poor solvent is between 98/2 and 90/10.9. The correcting fluid according to claim 1, having a pH of between 7and
 11. 10. The correcting fluid according to claim 9, having a pH ofbetween 7.5 and
 10. 11. The correcting fluid according to claim 1,wherein the opacifying pigment includes white pigments.